In the past, considerable difficulty has occured in assembling tanks in attempting to align the nozzle or top operator guide located in the top of the tank with the outlet valve located in the bottom of the tank. An operating rod extends through the nozzle to operate the lading valve in the tank bottom. This method of building tanks often results in a vertical multi-directional misalignment between the nozzle and the lading valve of between 1/2.degree. to 3.degree..
Misalignment in turn causes the packing in the nozzle to be moved to one side due to the binding of the upper part of the operating rod in the nozzle, enabling commodity to bypass the packing. This also reduces the service life of the packing, valve stem and sleeve.
One way to avoid this alignment problem is to use a solid rod fixture bolted to the bottom of the tank which establishes and protrudes through the opening in the top of the tank and which receives the nozzle prior to tack welding the nozzle to a nozzle reinforcing pad. However, the use of this heavy rod fixture is awkward.
Workmen with gun sights located on top of the tank have also attempted to sight a target located on the bottom outlet mounting flange in the tank bottom, and tack welding the nozzle to the nozzle reinforcing pad when the target is sighted. However, such sighting is time consuming, particularly in limited lighting in tank assembly plants which makes this technique difficult. It is even more difficult when shifts are operating during the darkness hours.